Below are common reasons why a Virtual Server connection may not be established properly:

1. Due to incorrect network settings on the Virtual Server side, the Syn Ack response from the Exchange Trading System to the TCP connection request cannot be received, preventing the connection from being established.
2. If Login is not performed within 13 seconds after TCP connection is established, the connection is disconnected by arrowhead.
3. Due to incorrect NAT settings on the Virtual Server side, messages do not reach arrowhead, or the port number assigned to the Virtual Server cannot be fixed, indicating errors in network configuration.
4. The Message Sequence Number at Login is not "1".
5. The Login request message is invalid, causing the connection to be disconnected. The ESP header often does not conform to the specifications in System Interface Specifications for arrowhead.
6. When Market Administration messages are sent from arrowhead at the same time as Login, the Virtual Server cannot properly receive these messages, resulting in a disconnection due to a timeout.
7. After a successful Login, since there is a period of more than 60 seconds during which the Virtual Server does not send any messages, a timeout occurs.
8. The IP address and port number of the Virtual Server have not been applied for or approved for production operation (limited to weekdays production).
9. When connecting to the Test Environment, you are connecting to a different environment than intended (e.g., confusing Test Environment A and B).